Apparatus for heating and recovering underground oil



Jan. 7, 1969 o. L. RILEY ET AL 3,420,301

APPARATUS FOR HEATING AND RECOVERING UNDERGROUND OIL Filed Dec. 5, 1966 FIG] ATTORNEY United States Patent 6 Claims ABSTRACT OF THE DISCLOSURE Apparatus for heating and reducing the viscosity of of hydrocarbons in an oil well comprising a tubing string of individual sections, a pump in one of the sections, an electrical heater with a pair of concentric spaced apart carbon electrodes mounted within one of the sections, the electrodes heating the fluid in the vicinity of an oil producing formation of the well. This electrical heating, accomplished by applying a voltage across the concentric electrodes, aids recovery of highly viscous oil in underground formations, such as oil sands, oil shale or tar sands, by permitting the oil to flow more readily for recovery by known flow or pumping methods.

This invention relates to apparatus for recovering hydrocarbon material from an underground formation which may be in the form of oil sands, oil shale or tar sands. The invention pertains more particularly to apparatus for the recovery of highly viscous oil, or other hydrocarbon materials that are substantially non- ;flammable under existing conditions.

This invention constitutes an improved apparatus for supplying heat in the form of a fluid medium to an underground formation containing tar sands, oil sands or oil shales for the purpose of increasing the oil recovery therefrom, and is applicable to all formations containing oil of high viscosity which may be non-flammable under present conditions and to those containing low to medium viscosity oils of which varying amounts may have been recovered by conventional means.

The primary production of petroleum hydrocarbons from oil-bearing formations is usually effected by drilling through or into the oil-bearing medium and providing access to the formation around the borehole so as to permit oil to flow into the borehole from which it may be recovered by conventional methods. If the formation contains an oil of low or medium viscosity at reservoir conditions, the well may be produced either by flowing or pumping in a manner well-known in the art, If, on the other hand, the formation contains a highly viscous oil at reservoir conditions, it may be necessary to heat the formation in the vicinity of the borehole to reduce the viscosity of the oil so that the oil may flow into the borehole. In time, even the wells containing free-flowing oil of low viscosity become depleted although a substantial amount of oil still remains in the producing formation underground. The residual oil left in the formation underground is very difficult to produce and considerable research has been carried out on secondary methods of recovering this residual oil. Various methods have been devised, such as heating, underground combustion, flooding with water or a miscible fluid, etc.

The heating of underground formations for the primary or secondary recovery of a hydrocarbon material such as oil presents may problems. In order to heat the underground formation a fluid is heated to the required temperature on the surface and pumped down through the borehole to the vicinity of the oil bearing formation. A

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major problem of this method is the dissipation of the heat between the surface and the oil bearing formation. Where great distances are encountered between the surface and the oil bearing formation virtually all of the heat is lost before it ever reaches the producing formation. In view of this the heating of a fluid on the surface and the subsequent pumping of the heated fluid through a borehole to the oil producing formation is impractical except for very shallow wells. This is so whether the heated fluid is water, oil or steam. In order to solve this problem, attempts have been made to design an apparatus for heating the hydrocarbon material in situ; however, such attempts have, to a large degree, been unsuccessful because the size of the heating apparatus has been too bulky and cumbersome to be lowered into a borehole casing of average diameter without undue crowding. This is particularly true when other piping, such as a production line, is needed to occupy a portion of the space in the casing.

This invention solves the aforesaid problems by providing a heating means of compact design adapted to be situated within the borehole casing adjacent the oil-bearing formation. The heating means is capable of allowing hot or cold water to be pumped into the oil-bearing formation for changing the viscosity of the oil and having further means therein for retrieving the lower viscosity oil.

Another object is to provide an apparatus for electrically heating a fluid at any point in a borehole.

Another object is to provide an electrical heater that is designed to fit within a borehole casing.

Another object is to provide an apparatus for heating water, imparting the heated water to an oil-bearing formation and exhausting the heated water and oil to the top of a borehole casing.

Another object is to provide a means for heating water efliciently and economically Within a minimum heat loss.

Another object is to provide a modular electric heating unit that can be connected to additional heating units to form an integral heating unit of varying size and capacity.

These and other objects and novel features of the present invention will be more clearly and fully set forth in the following specification, claims and attached drawings. A preferred embodiment of this invention will now be described with particular reference to the accompanying drawings wherein:

FIG. 1 is a vertical sectional view diagrammatically illustrating an oil well with a heater therein embodying the features of the present invention;

FIG. 2 is an enlarged fragmentary longitudinal section through the heater showing the operative relationship of the various components thereof; and

FIG. 2a is a sectional view along line 2a2a of FIG. 2.

Referring now to the drawings wherein like reference numerals designate like or corresponding parts through out the several views, there is shown in FIG. 1 a casing 10 having a plurality of orifices 11 along a portion thereof adjacent the oil-bearing formation. The casing 10 is inserted into a borehole and extends upward beyond the surface. Mounted within the casing 10 is a tubing string 12, which consists of a plurality of cylindrical sections of pipe joined together along their ends to form a continuous length of tubing. Extending substantially through the length of the tubing string 12 is a sucker rod 13, which is adapted to actuate a rod pump 14. In order to actuate the rod pump 14, the sucker rod 13 is reciprocated in a vertical direction by a drive means (as shown at the top of FIG. 1). The details of the rod pump 14 and the drive means are not shown for the sake of brevity and simplicity, since they do not constitute a part of this invention. The apparatus as described above is commonly used in the oil producing industry in order to cause low viscosity oil to be brought to the surface. However, as mentioned hereinabove, when the viscosity of the oil increases, this commonly used method and apparatus become inefficient and inoperable because the oil becomes tooviscous to pump and the orifices 11 in the casing become clogged by solidified paraffin or other solidified constituents of crude oil and the like.

In order to dissolve the solidified materials clogging the orifices 11 and to lower the viscosity of the oil, heat should be applied to the oil-bearing formation. While this is well-known and has been attempted in the past by pumping steam, hot water or oil into the borehole from the surface, it has proven to be a highly inefficient though desirable procedure. The reason for the inefliciency is the high rate of heat loss as the heated fluid travels through the borehole to its point of application. The loss of heat as the fluid travels through the borehole means quite often that by the time the fluid reaches the oil bearing formation it is cold or at best luke warm. Additionally, it is virtually impossible to calculate the heat loss and therefore extremely diflicult to control or determine the actual temperature of the fluid at the bottom of the borehole. Attempts have been made to produce steam in elaborate, expensive and bulky boiling apparatus on the surface and subsequently pump the steam down the borehole in order to obtain hot water at greater depths. This has proven to be an expensive and uncontrollable procedure. In order to eliminate the aforementioned problems, this invention provides a compact instantaneous electric water heater mounted within a section of the tubing string 12 and forming an integral part thereof.

The heater 15 comprises a complete cylindrical section of the sections of pipe forming the tubing string 12. By limiting the heater 15 to a single section it can be removed or installed on the tubing string quickly and easily as hereinafter described. Additionally, a plurality of heaters 15 can be joined end to end to form a continuous heater of varying capabilities and heating capacity. Since all sections of pipe comprising the tubing string 12 have substantially identical external configurations and attaching means, the heater sections can be interplaced anywhere along the tubing strings length. If the heater 15 is placed above the rod pump 14, the sucker rod 13 will pass through an orifice therein. However, it is the preferred embodiment of the invention to have the heater 15 secured beneath the rod pump 14 on the bottom of the tubing string 12, as shown in FIG. 1.

FIG. 2 illustrates the heater 15 which comprises a cylindrical section of pipe 16 which forms a section of the tubing string 12. The external surface of the pipe 16 adjacent both the upper and lower ends thereof has a threaded portion 17. When it is desired to assemble the tubing string 12 or to add additional heaters, a threaded coupling 18 is used to secure together the various sections of pipe. All the sections of pipe comprising the tubing string 12 have complementary threads on each end thereof. It will be obvious from the above description that any number of heaters 15 can be secured together at any point along the tubing string 12. The internal walls of the heater pipe 16 are coated with a suitable insulation, such as a high dielectric phenolic resinoid 18 or the like, in order to reduce the electrical ground loss of the heating unit to a minimum. While many types of commercially available insulations may be used successfully, phenolic resinoid is preferred because of its high thermal shock resistance and its compatible co-eflicient of expansion with the heater pipe 16. In view of the compatibility of expansion and retraction between the phenolic resinoid 1'8 and the heater pipe 16, the phenolic resinoid 18 is substantially prevented from breaking loose from the internal wall of the pipe 16 during the heating and cooling stages. Secured to the phenolic resinoid liner 18 is a cylindrical carbon electrode 19. Mounted concentrically within the carbon electrode 19 in spaced complementary relationship thereto is a second carbon electrode 20. The carbon electrode 20 is of a cylindrical configuration having an orifice 21 coaxially therein. The carbon electrodes 19 and 20 are held in their complementary spaced relationship by a plurality of spacers 22. The spacer-s 22 are constructed from a suitable insulating material and are fixedly secured between the outer electrode and the inner electrode 20 in a manner so as to keep the electrodes, in spaced relationship, without impeding the flow of fluid between the electrodes. Electrically connected to the outer electrode 19 and the inner electrode 20 are individual electrical power conductors 23. The conductors 23- extend upwardly through an insulated cable 24 mounted within the tubing string 12. The conductors 23 extend above the surface opening to the borehole to a control panel to which a power source is connected.

In order to insure the eflicient and complete transmission of electrical energy from the power conductors 23 through the entire surface of the carbon electrodes 19 and 20, the electrodes are impregnated with an electrically conductive material such as copper or aluminum powder. However, in lieu of the impregnation of the carbon electrodes 19 and 20 with a metal powder, a fine interconnected screen, constructed from an electrically conductive material, can be utilized. The carbon electrodes 19 and 20 are slightly longer than the pipe 16 within which they are mounted. In view of their length, the carbon electrodes extend beyond the ends of the pipe 16. The extension of the carbon electrodes 19 and 20 beyond the confines of the pipe 16 is important when more then one heater is desired to be utilized. When additional heaters are required or desired, the auxiliary heater is placed in abutt-ing coaxial relationship to the primary heater, so that the inner and outer electrodes 20 and 19 respectively of both heaters are also in abutting coaxial engagement. In this maner, the electrical power that is supplied to the primary heater through power conductors 23 is transmitted through the impregnated carbon electrodes in the primary heater to the impregnated carbon electrodes of the auxiliary heater. The heaters, as mentioned hereinbefore, are maintained in the complementary relationship by the threaded coupling 18.

In operation the tubing string 12 is assembled, including the rod pump 14 and as many heating units 15 as desired. The heating units 15 can be mounted in the tubing string 12 either above or below the rod pump 14. If the heating units 15 are mounted below the pump 14, a plurality of orifices must be located on the tubing string 12 above the pump 14 in order to allow the heated material to enter the string and be pumped upwardly. If the heating units 15 are mounted above the rod pump 14, the sucker rod 13 will extend through the orifice 21 in the inner carbon electrode 20. The tubing string 12 is inserted into the borehole in a manner well-known to those skilled in the art. Water, oil or any other fluid is poured or pumped down through the casing string 12. When the fluid is flowing through the casing string 12 in the vicinity of the heating units 15 the power source is turned on. The electrical power is controllably conducted through the power conductors 23 to the carbon electrodes 19 and 20 based upon the electrical interaction between the carbon electrodes 19 and 20. By varying the rate of flow of the fluid, the number of heating units 15 or the effective area of the carbon electrodes 19 and 20, the temperature of the water can be controlled and, if desired, steam can be generated. The generation of steam is desirable under certain conditions when the dissolving of salts is required.

It will be obvious to those skilled in the art that apparatus of heating hydrocarbon material in situ, for lowering the viscosity thereof, has been described, which will enable greatly increased recovery from wells that are substantially non-flow-able under existing conditions. While a preferred embodiment has been described in detail, it is to be understood that modifications may be made, e.g. that the heater which is placed directly adjacent and below the pump in the preferred embodiment may be placed adjacent and above the pump below ground level at the oil-bearing stratum, without departing from the spirit and scope of the invention as defined in the claims which follow.

We claim:

1. An apparatus for heating and reducing the viscosity of hydrocarbons in an oil well comprising:

a tubing string having a plurality of individual sections;

a pump mounted within one of said sections;

sucker rod means for actuating said pump;

a heater above said pump having a pair of concentric carbon electrodes which are spaced apart and mounted within one of said sections, said sucker rod means extending through a bore in the inner electrode of said pair; and,

means for applying a voltage across the electrodes for actuating said heater.

2. An apparatus in accordance with claim 1 wherein said heater comprises:

a cylindrical outer carbon electrode secured to the inner surface of one of said sections of said tubing string;

a cylindrical inner carbon electrode secured within said outer carbon electrode in concentric spaced relationship thereto; and,

means for electrically actuating said inner and outer carbon electrodes.

3. An apparatus in accordance with claim 1 comprising:

means for mounting additional heaters on said tubing string.

4. An apparatus in accordance with claim 2 wherein said inner and outer carbon electrodes are impregnated with an electrically conductive material.

5. An apparatus in accordance with claim 2 wherein said outer carbon electrode is separated from said inner surface of said tubing string by a coating of phenolic resinoid.

6. An apparatus for heating and recovering hydrocarbons from an oil well comprising:

a tubing string having a plurality of individual externally symmetrical sections;

means for joining said sections together in coaxial complementary relationship;

a pump mounted within one of said sections;

sucker rod means for actuating said pump;

a heater above said pump having a pair of concentric spaced carbon electrodes which are spaced apart and mounted within one of said sections;

said carbon electrodes extending beyond the upper and lower edges of said section and said sucker rod rneans extending through a bore in the inner electrode of said pair; and,

means for applying a voltage across the electrodes for actuating said heater by supplying electrical power to said carbon electrodes individually.

References Cited UNITED STATES PATENTS 495,936 4/1893 Gardner 166-60 678,813 7/1901 Hill 219291 884,424 4/ 1908 Seymour et a1 166-60 1,184,200 5/1916 Nash 219-292 1,774,381 8/1930 Kiefer 252-503 2,350,429 6/1944 Troupe 166-60 2,525,314 10/1950 Rial 166-60 2,836,699 5/1958 Mullin 219 -292 X 2,954,826 10/1960 Sievers 166-60 3,213,942 10/1965 Nixon 16660 CHARLES E. OCONNELL, Primary Examiner.

I. A. CALVERT, Assistant Examiner.

US. Cl. X.R. 

